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28356 results in Astrophysics

Page 63 of 1418

  • The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey—II. Survey status, pulsar census, and first pulsar discoveries

  • N. D. R. Bhat, N. A. Swainston, S. J. McSweeney, M. Xue, B.W. Meyers, S. Kudale, S. Dai, S. E. Tremblay, W. van Straten, R. M. Shannon, K. R. Smith, M. Sokolowski, S. M. Ord, G. Sleap, A. Williams, P. J. Hancock, R. Lange, J. Tocknell, M. Johnston-Hollitt, D. L. Kaplan, S. J. Tingay, M. Walker
  • Journal:
    Publications of the Astronomical Society of Australia / Volume 40 / 2023
    Published online by Cambridge University Press:
    11 April 2023, e020
    • Article
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  • In Paper I, we presented an overview of the Southern-sky MWA Rapid Two-metre (SMART) survey, including the survey design and search pipeline. While the combination of MWA’s large field-of-view and the voltage capture system brings a survey speed of ${\sim} 450\, {\textrm{deg}}^{2}\,\textrm{h}^{-1}$, the progression of the survey relies on the availability of compact configuration of the Phase II array. Over the past few years, by taking advantage of multiple windows of opportunity when the compact configuration was available, we have advanced the survey to 75% of the planned sky coverage. To date, about 10% of the data collected thus far have been processed for a first-pass search, where 10 min of observation is processed for dispersion measures out to 250 ${\textrm{pc cm}}^{-3}$, to realise a shallow survey that is largely sensitive to long-period pulsars. The ongoing analysis has led to two new pulsar discoveries, as well as an independent discovery and a rediscovery of a previously incorrectly characterised pulsar, all from ${\sim} 3\% $ of the data for which candidate scrutiny is completed. In this sequel to Paper I, we describe the strategies for further detailed follow-up including improved sky localisation and convergence to timing solution, and illustrate them using example pulsar discoveries. The processing has also led to re-detection of 120 pulsars in the SMART observing band, bringing the total number of pulsars detected to date with the MWA to 180, and these are used to assess the search sensitivity of current processing pipelines. The planned second-pass (deep survey) processing is expected to yield a three-fold increase in sensitivity for long-period pulsars, and a substantial improvement to millisecond pulsars by adopting optimal de-dispersion plans. The SMART survey will complement the highly successful Parkes High Time Resolution Universe survey at 1.2–1.5 GHz, and inform future large survey efforts such as those planned with the low-frequency Square Kilometre Array (SKA-Low).

  • 9 - Ex-Stars

  • Marc Pinsonneault, The Ohio State University, Barbara Ryden, The Ohio State University
  • Book:
    Stellar Structure and Evolution
    Published online:
    02 May 2023
    Print publication:
    06 April 2023, pp 209-230

  • Summary

    As Russell and Vogt pointed out in the 1920s, the properties of a main sequence star depend crucially on its mass. After the main sequence, the star’s mass is also vitally important in determining its physical properties. Will helium burning begin or not? If it begins, will it begin with a flash? Will carbon burning begin or not? The answers to these questions, as we have seen, depend primarily on the star’s mass.

  • 4 - Stellar Energy Transport

  • Marc Pinsonneault, The Ohio State University, Barbara Ryden, The Ohio State University
  • Book:
    Stellar Structure and Evolution
    Published online:
    02 May 2023
    Print publication:
    06 April 2023, pp 64-88

  • Summary

    When investigating a political scandal, the standard advice is “follow the money.” When investigating stellar structure, a comparably useful piece of advice is “follow the energy.” Since energy cannot be created or destroyed (if we regard mass as a sort of congealed energy), forensic investigation of a star’s energy content will uncover whatever physical processes are hidden in a star’s opaque interior.

  • 3 - Equations of State

  • Marc Pinsonneault, The Ohio State University, Barbara Ryden, The Ohio State University
  • Book:
    Stellar Structure and Evolution
    Published online:
    02 May 2023
    Print publication:
    06 April 2023, pp 43-63

  • Summary

    Because stars are large and massive compared to a rocky planet like the Earth, we expect that a balance between pressure gradients and gravity inside a star will require very high internal pressure. However, there can be very different ways in which high pressure can be achieved, as two examples from the Earth make clear. Both the atmosphere and the oceans are in hydrostatic equilibrium; air pressure thus decreases with altitude above sea level, while pressure in the ocean increases with depth.

Page 63 of 1418